It has long been a problem in the textile industry to create an inexpensive, sewable fire resistant thread. The sewing thread should allow easy movement when tension is applied and ease in needle threading; should resist friction during sewing; should have sufficient elasticity to avoid the breaking of stitches; and should have sufficient strength to hold seams during laundering or dry cleaning and in use. Threads for special uses may require appropriate treatment. Garments made of fire-resistant fabrics, for example, may be sewn with thread that has also been made fire-resistant.
Such a thread would have a variety of uses including, but not limited to: sewing mattress parts together, sewing fire fighting gear and clothing together, and sewing upholstery together. Additional uses for such a sewable thread include, but are not limited to, seat belts, air bags, cargo nets, cargo straps, and carpeting. A sewable fire resistant thread must meet the federal requirements of 16 CFR 1632 and Cal 129 in order to be used to sew the various components of a mattress together. Currently, thread comprised of Kevlar® strands throughout is employed having satisfactory results. However, Kevlar® is very expensive making a cheaper alternative economically attractive.
U.S. Pat. No. 7,111,445 discloses a fire resistant core-spun yarn which may be used as a sewing thread. The patent discloses a fire resistant composite yarn comprising an elongating central core (e.g., cotton, polyurethane, polyester, nylon), a non-elongating bottom cover (e.g., fiberglass, ceramic, or aramid fibers) over the core, and an outer cover (e.g., polyester or nylon) over the bottom cover, all of which are treated first with a bonding agent followed by treatment with a lubricant.
U.S. Pat. Nos. 6,800,367 and 7,087,300 each disclose a fire retardant and heat resistant yarns containing oxidized polyacrylonitrile fibers, high strength filaments, and/or strengthening fibers. They each disclose a fire retardant and heat resistant yarn suitable for making fabric comprised of one or more yarns wound in a spiral helix.
Hence, there exists an unsatisfied need for an inexpensive, sewable fire resistant thread.